Sorry for my delay in getting back to you. You may change a device rate plan via our portal. You would go to devices tab, find your device select the pencil icon for edit, you will then see a drop down which includes "Rate plan and pool name".
When you select this drop down a new pop up box will appear with information on selected device. If you select the down arrow in the "Rate plan" box you will see all available rate plan options for this device.